Some design strategies please

[markocosic]

On 05/06/2023 at 10:28, SteamyTea said:

seems that is a benefit of wood fibre board and cellulose insulation.

 

They sell woodfibre as sound attenuation. I think it's this absorbent surface rather than the "hollowness" of drylining per se that creates the audio effect.

[saveasteading]

3 hours ago, markocosic said:

think it's this absorbent surface rather than the "hollowness" of drylining per se that creates the audio effect.

Correct. It is the hardness of the surface of plasterboard, or plaster,  that reflects the sound. If walls are parallel, as most are,  there is added echo. Fibreboard is much softer and more absorbent, but not usually a suitable finish.

 

The hollowness, esp with mineral wool,  aids dampening between rooms but not within a room.

[SteamyTea]

1 hour ago, saveasteading said:

Correct

Almost.

It is the stiffness.

As 'sound' is really just a mass of air moving, it has kinetic energy.

If it hits something that can easily bend, then some of that kinetic energy is absorbed, and ultimately converted to thermal energy, which is then radiated back out at a different frequency.

You can, with a very stiff material, set up a room that would, for a fixed sound source and frequency, in such a manner that the reflected sound will interfere with the source and cancel itself out.  The room will heat up though.

One of the reasons that foams absorb sound so well is that they have unevenly sized and spaced voids in them, this sets up interference at the micro level.  Some neoprenes, like wet suit material, can be very effective for very little added thickness.

The other main reasons is that they are flexible, this allows the voids to change shape and size when compressed, absorbing a greater range of frequencies.

 

Edited July 19, 2023 by SteamyTea

[saveasteading]

3 hours ago, SteamyTea said:

Almost.

It is the stiffness.

Tomorrow I may look up the definitions of hardness and stiffness.

 

I was once given a tour of a uni  acoustics dept.

In the anechoic chamber they did the gun thing, which just sounded ph.

In the echoic chamber it was impossible to talk. The walls weren't only parallel and super hard (stiff) but some calculated distance apart to increase the reverberation.

[Temp]

22 hours ago, saveasteading said:

Tomorrow I may look up the definitions of hardness and stiffness.

 

I was once given a tour of a uni  acoustics dept.

In the anechoic chamber they did the gun thing, which just sounded ph.

In the echoic chamber it was impossible to talk. The walls weren't only parallel and super hard (stiff) but some calculated distance apart to increase the reverberation.

 

Southampton? My lads going back to Southampton for his 3rd and 4th years in September.

[saveasteading]

Not Southampton.  It was a very long time ago. 

[JohnMo]

1 minute ago, Plover said:

more durable than drywall.

Must say have lived in dry lined walled houses for over 30 years, and poor durability of the plasterboard has never been an issue, I have witnessed - in my house or anyone else's.

 

Been used in England since the late 70s I believe, but mostly in a commercial setting, where if it wasn't durable, that would be more an issue.